1. Field of the Invention
The present invention relates to a valve apparatus and especially relates to a supercharged pressure control valve apparatus for regulating abnormal pressure rise in an upstream part of an air suction path of a throttle valve, which may occur at closing the throttle valve for deceleration.
2. Description of the Prior Art
A conventional supercharged pressure control valve apparatus used in an internal combustion engine, for example, shown in Published Unexamined Japanese Utility Model Application Hei 1-58723 is described with reference to FIG. 3. FIG. 3 is a cross-sectional view showing the conventional supercharged pressure control valve apparatus. In FIG. 3, the conventional supercharged pressure control valve apparatus comprises: an air cleaner 1 serving as an air sucking portion; suction pipes 2 and 2 serving as paths of suction air from the air cleaner 1; a supercharger 3 connected to the suction pipes 2 and 2; a throttle valve 6 for controlling amount of the suction air; a decompression path 8; and a supercharged pressure control valve 9. In the suction pipe 2, the upstream part 4 of the supercharger 3 is a first suction air path and the downstream part 5 of the supercharger 3 is a second suction air path. The decompression path 8 connects the first and second suction air paths 4 and 5. The supercharged pressure control valve 9 controls the pressure of the supercharged pressure in the second suction air path 5 by opening and closing the decompression path 8.
Details of the supercharged pressure control valve 9 is described. The supercharged pressure control valve 9 comprises: a cylindrical housing 10; a second path formed in a wall part of the housing 10 for introducing the supercharged air in the second suction air path 5 to a second pressure chamber 29; and a flange 13 formed on the lower end of the housing 10 and mounted on a mounting part 14 of the suction pipe 2 serving as the second suction air path 5. Furthermore, a valve seat 15 is formed on an inner wall of the housing 10 and around an opening 13a of the flange 13. A nipple part 16 of the housing 10 serving as an inlet and an outlet of the suction air is connected to the suction pipe 2 serving as the first suction air path 4. A disc-shaped diaphragm 17 is sealed at its outer periphery by a cup-shaped casing 18 and circular periphery of top end of the housing 10. A first pressure chamber 19 is formed by the diaphragm 17 and the casing 18. A first path 20 connects an output port 21 and a nipple 22 for introducing the supercharged air in a third suction air path 7 to the first pressure chamber 19. Plate-shaped holders 23a and 23b sandwiches the center part of the diaphragm 17 and an end of a rod 24 is connected at the center of the holders 23a and 23b. The valve disc 25 for opening and closing the decompression path 8 is connected to the other end of the rod 24 and formed to contact with the valve seat 15. The rod 24 is slidably born by a bearing 26 and the bearing 26 is supported by a bearing holder 27. A spring 28 is compressedly provided between the casing 18 and the holder 23a for supplying an elastic force to the inside bottom of the diaphragm 17 in a direction of close the valve 9. The second pressure chamber 29 is formed between the diaphragm 17 and the bearing holder 27 and connected to the second suction air path 5 by the second path 11. A throttle 30 is formed in the second path 11 which serves as an air resistance for making a transfer lag of the pressure in the second path 11.
In the above-mentioned conventional supercharged pressure control valve apparatus, a seal member 23b is necessary to keep the sealing of the casing 18 and the housing 10. Thereby the number of parts and components constituting the apparatus is great and the work-ability to assemble the casing 18 on the housing 10 is not good. Furthermore, the supercharger 3 and the supercharged pressure control valve 9 are independently disposed and connected by the suction pipe 2. As a result, a large space is necessary to provide the conventional apparatus. Furthermore the conventional apparatus needs plural pipes for making the by-pass air path (decompression path 8) and thereby, the cost for making the conventional apparatus is expensive.